As I said before, I will use the original NES controller as a remote. And today the controllers arrived. These where also bought at Ebay for 150 SEK ~ 25 USD.
Since I want the ability to easily change the controller if it breaks I will not convert the controller to USB as many other have done with help of www.retrousb.com. I will convert the port on the NES instead and as a bonus I will keep the outside of the console untouched.